[SOLVED] how to call form.showdialog()?

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Working on building a Tabbed Webbrowser using CEF. It works properly until trying to create a new Window(new Form) from the a class that implements ILifeSpanHandler to catch new window events. It works when calling Form.Show() but fails when calling Form.ShowDialog() as this is being called from a different Thread. Is their a way to call ShowDialog() on new windows from another thread?

Here is how the call looks.

C#

public bool OnBeforePopup(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, string targetUrl, string targetFrameName, WindowOpenDisposition targetDisposition, bool userGesture, IPopupFeatures popupFeatures, IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser newBrowser)
{
    newBrowser = null;

    PopupWindow popup = new PopupWindow()
    {
        Url = targetUrl
    };
    popup.Show();
}

After @graeme_grant help and google have come up with a solution to use show() to act as a ShowDialog(). Below is a working solution to the problem.

C#

public bool OnBeforePopup(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, string targetUrl, string targetFrameName, WindowOpenDisposition targetDisposition, bool userGesture, IPopupFeatures popupFeatures, IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser newBrowser)
{
    newBrowser = null;
    //A big thanks to Graeme_Grant for his help 
    //with the Dispatcher.Execute(Action) example
    Dispatcher.Execute(() => 
    {
        Form form = MainWindow.ActiveForm;
        PopupWindow popupWindow = new PopupWindow()
        {
            Url = targetUrl,
            Width = 1000, 
            Height = 1000,
        };
        //Will not work properly with ShowDialog()
        //Shown/FormClosed EventHandlers are used for 
        // a workaround for ShowDialog() behavior
        popupWindow.Shown += delegate 
        { 
            form.Enabled = false; 
        };
        popupWindow.FormClosed += delegate 
        { 
            form.Enabled = true; 
        };                
        popupWindow.Show();
    });

What I have tried:

Tried calling form.ShowDialog() over Form.Show()

Posted 26-Jul-24 14:32pm

charles henington

Updated 31-Jul-24 14:50pm

v2

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Graeme_Grant · Accepted Answer · 2024-07-26T23:43:00

If you're not on the UI thread, then you need to switch back.

Here is an example where I have a helper class that works with the MainForm:

C#

namespace System.Windows.Threading;

public static class DispatcherHelper
{
    public static void Execute(Action action)
    {
        // no cross-thread concerns
        if (Application.OpenForms.Count == 0)
        {
            action.Invoke();
			return;
        }

		try
		{
			if (Application.OpenForms[0]!.InvokeRequired)
                // Marshall to Main Thread
				Application.OpenForms[0]?.Invoke(action);
            else
                // We are already on the Main Thread
                action.Invoke();
        }
		catch (Exception)
		{
			// ignore as might be thrown on shutting down
		}
    }
}

Then to use:

C#

DispatcherHelper.Execute(() => [run code here]);